In a wireless mobile network, for example a Long Term Evolution (LTE) network, a user equipment (UE) latches onto a base station (BS) for admission to a coverage area. Such a procedure is referred to as an Initial Network Access Procedure (INAP). The INAP occurs by first measuring, by the UE, a comparative Signal Power-Level (SPL) of available base stations and identify suitable target base stations. The UE then performs sync by reading a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) to get cell-ID, frame-sync. After sync, the UE reads the target base stations cell-broadcast information (or Network Access Related Information (NARI)) upon wait for a periodic broadcast. After reading the NARI, the UE sends an Initial Network Access Message (INAM) to the target base stations. In response, the UE obtains an Initial Network Access Response (INAR) from the target base stations. The INAR includes uplink grant (ULG) resource allocation provided by a network to the UE to send an uplink message to continue the INAP procedure. The UE subsequently transmits a Connection Setup Request (CSR) using INAR to the target base stations, to continue the INAP procedure. In response to the CSR, the UE may receive from the target base stations, a Connection Setup (CS) in case necessary resources have been granted for latching to the target base stations. Otherwise, the UE receives a Connection Reject (CR) from the target base stations.
The above INAP procedure, however, faces different issues. For example, it is difficult to identify a single suitable BS based on the comparative SPL as the target base stations may not have capacity to provide service to the UE due to resource availability, existing load or other issues. Hence, there are latching delays or failures and post-latching service quality issues of the UE to the target base stations.
There is a delay in latching due to wait for receipt of the cell-broadcast information which is further likely to delay latching-on. Also, the INAM request with same sequence number from multiple UEs to the same target base stations is likely to lead to successful processing of first request and discarding of remaining INAM requests (also termed as INAM collision). There is hence a delay in the INAP procedure due to repeat attempts or NAP failure.
Delayed or unsuccessful latching due to constraint of single BS is another issue faced during the INAP procedure. The UE sending CSR to a single BS may lead to unsuccessful latching (receipt of CR), in case the BS has resource constraint or any other constraint. This happens due to that fact that the UE does not have visibility on factors like network resource availability, existing-load-conditions, and the like, of the BS. There is hence a delay in latching process or complete latching failure with the BS, due to repeat unsuccessful attempts by the UE.
Post successful latching, the UE may find issues with service quality such as below par service for existing services or new service denial. Further, every unsuccessful step to latch on a single BS leads to multiple reattempts of the step before sequential attempting the next BS. Waiting time at each unsuccessful step of every sequential latching-attempt cumulatively increases the delay in the latching procedure.
The UE waits for NARI once the sync is done with the BS. However, the BS broadcasts the NARI in a fixed time interval and hence the UE has to wait till next broadcast available which leads to delay in latching. Moreover, the UE waits for NARI. In case, the BS goes to shut down because of some issue or maintenance and stops sending the NARI, the UE will keep on waiting until wait-time-out, leading to unnecessary delay in latching.
The above issues further increase if the number of UEs in the coverage area increases. In an improvement to the existing INAP procedure, use of required information (NARI) for sending INAM is suggested. However, wait time for availability of such information can be variable. In another improvement to the existing INAP procedure, BS suitability assessment based on SPL is addressed, however without considering network conditions (for example, capacity and load-condition of the BS). This leads to multiple unsuccessful attempts during the latching procedure and post latching usability problem.